This paper introduces an automated dynamic frequency scanning tool designed to predict stability in power systems. The tool integrates frequency scanning and stability analysis into a single, user-friendly platform, which is validated through Electromagnetic Transients (EMT) simulations and traditional small-signal stability techniques. Case studies involving a modular multi-level converter (MMC) system are conducted using two grid-forming (GFM) controller strategies: voltage-source type and current-source type virtual synchronous generators (VSGs). The effectiveness of the tool is demonstrated by comparing stability predictions from the scanning method with results from root locus analysis and EMT simulations, showing that it provides a reliable and efficient approach for predicting system stability. A key contribution of this paper is the comparative analysis of the two GFM controller types, offering valuable insights into their performance and stability characteristics. The results highlight that the current-source type VSG can operate effectively in a strong ac system, which is a challenge typically faced by the voltage-source type VSG.

This paper presents a computationally efficient approach for estimating the power semiconductor losses of a modular multilevel converter (MMC) in electromagnetic transient (EMT) simulations. Earlier approaches required the loss estimation to be carried out at the individual IGBT-diode component level. In contrast, this paper extends this concept to the simulation of an entire MMC arm thus speeding up the simulation significantly. The proposed approach can accurately estimate the losses during steady state as well as transient operation with great speed. Furthermore, the loss estimates of each individual submodule can also be reported separately with the proposed approach, if needed. It is verified using a simulation test case of a two-terminal MMC-HVdc link and comparing the computed losses against the earlier (but much slower) approach of computing the losses at individual switch level.

Estimating the electrical model parameters of photovoltaic (PV) modules, which are normally not provided by manufacturers, is crucial for modeling PV systems in simulation studies. This work proposes a novel robust approach to identify parameters of the single diode model (SDM) of a PV module. The equivalent electrical circuit parameters are extracted by solving a set of equations through the application of the Lambert W function for a given value of ideality factor, Ai, based on data found in manufacturer's datasheets under standard test conditions (STC). To find the optimal ideality factor, parameters are computed for different Ai values within a defined range, and their fitness is assessed using a multi-criteria objective function. Irradiance and temperature dependence of the parameters are estimated using the temperature coefficients available on datasheets and the irradiation coefficient of open circuit voltages, calculated using the data at Normal Operating Cell Temperature (NOCT). By utilizing the estimated values for the parameters, the current-voltage (1- V) characteristics at different levels of irradiation and temperatures, and the temperature coefficient of maximum power for several PV modules, were obtained. The errors expressed in terms of root means square deviations compared to the datasheet values were less than 4 % for the five different PV modules considered.

The principle of duality is applied for electromagnetic transient (EMT) modeling of industry scale (i.e. 50, 390 MVA) multilimb transformers. While saturation, hysteresis, deep-saturation, and remanent flux are accounted for, the need for transformer internal design information such as core dimension or material is eliminated. This is achieved by formulating the equivalent circuits with an alternative set of parameters that are either provided by the manufacturer or can be determined using conventional techniques. Open-circuit tests confirm that the models produce accurate excitation currents at different saturation levels when compared with measurement results. Furthermore, the models facilitate correct short-circuit condition with support for arbitrary number of windings. Upon validating the models, inrush current is simulated and the worst-case scenario is determined due to potential remanent flux values. The findings agree with an established EMT simulation model as well as manufacturer analytical approximations. Simulated hysteresis loops are also investigated.

This paper presents a technique, implemented in an EMT type software, utilizing multiple cores of a processor, to simulate a single interconnected electrical power system. In this technique, large networks are split into smaller ‘subsystems’ by using the natural propagation delay introduced by transmission lines. This method does not introduce time step delays between subsystem solutions and hence yields computational results perfectly in agreement with the traditional non-split simulations. Proprietary and confidentiality issues arising from different vendors collaborating on large scale power system studies can also be resolved using the proposed technique.

This paper proposes a parallel multimodal optimization algorithm that is combined with electromagnetic transient simulation in a platform that unifies the setup, test, and execution of optimal designs for power systems. The algorithm speeds up the design of power systems as its computations can be executed independently on a highly parallelized environment. Additional speedup is achieved by using a surrogate model to estimate the objective function in regions of suspected local optima. The estimated functions can be used in the subsequent stages of post-optimization studies, such as sensitivity analyses. Comparative studies, in terms of computation time, are conducted against sequential execution of the proposed algorithm. The optimal design of a VSC-HVDC transmission is described to demonstrate the capabilities of the proposed algorithm.

This paper presents a method to implement the Electromagnetic Transients (EMT) simulation algorithm on a multi-core or grid processing platform. The simultaneous use of multiple processors to divide and solve portions of the simulation has the potential to speed up the overall simulation significantly. However, communication bottlenecks can reduce its effectiveness. This paper uses the Electric Network Interface (ENI), which is a TCP based communication interface implemented using transmission lines (t-lines) as natural interface ports. ENI allows the sub-systems on either side of t-lines to be simulated on separate processors on both local host and distributed computers connected by standard local area networks (LAN). Using several implementation examples, it is shown that the communication bottleneck is significant when the execution time for each subsystem is small, and can result in slower simulations than on a single processor. However, with sufficiently large subsystems, there is significant speed-up to the overall execution time.

This paper compares the errors made when the saturation is modeled as a current source placed at the terminals of the transformer, rather than in between the primary and secondary leakage inductances. Such an approach is often used in nodal analysis based electromagnetic transient programs in order to increase the computational efficiency of transformer model. The results are satisfactory for most studies. However, there are some inaccuracies which can be observed in some situations. The paper also introduces a slight modification, where the saturation current injections can still be located at the terminals, but the injections can be calculated exactly as though the magnetizing branch is located in between the leakages. This approach can accurately represent magnetizing current in transformers without sacrificing the computational efficiency of the previous model. This new model is compared with the conventional model by conducting several simulations using PSCAD/EMTDC.

This paper presents a grid-processing approach that interfaces optimization algorithms with electromagnetic transients (EMT) simulations programs to significantly speed up the design of power apparatus and networks. A parallel gradient-based optimization algorithm feeds trial parameters to an EMT simulator to determine the optimal parameters. The considerable parallelism in the algorithm is exploited to construct a grid-processing based implementation. The paper discusses the methodology and compares the speedup gained over the conventional sequential approach. The results indicate that the approach is promising, with the speedup being often an order of magnitude or more.

The number of semiconductor switches in a modular multilevel converter (MMC) for HVDC transmission is typically two orders of magnitudes larger than that in a two or three level voltage-sourced converter (VSC). The large number of devices creates a computational challenge for electromagnetic transient simulation programs, as it can significantly increase the simulation time. The paper presents a method based on partitioning the system's admittance matrix and deriving an efficient time-varying Thevenin's equivalent for the converter part. The proposed method does not make use of approximate interfaced models, and mathematically, is exactly equivalent to modelling the entire network (converter and external system) as one large network. It is shown to drastically reduce the computational time without sacrificing any accuracy. The paper also presents control algorithms and other modelling aspects. The efficacy of the proposed method is demonstrated by simulating a point-to-point VSC-MMC-based HVDC transmission system.

This paper extends previous approaches that use electromagnetic transient simulation to estimate the switching and conduction losses of insulated-gate bipolar transistor-based voltage-sourced converters embedded in large electrical networks. In contrast to earlier approaches, which merely estimate and report the device loss, the proposed new model also reflects this loss back into the electrical network model using a controlled voltage source. Additionally, an improved representation of the semiconductor switch in the flexible AC transmission system controller is introduced. This new representation has a mathematically simpler form in comparison to earlier approaches and yet permits the use of a relatively large time step.

-This paper describes the development of an on-line discrete wavelet transform tool for an electromagnetic transient simulation program. Multi-resolution properties of wavelet transform make it ideally suitable for analyzing power system transient signals which consist of non-periodic high frequency oscillations superimposed on power frequency signal. New power system devices such as power quality monitors and protective relays based on algorithms involving wavelet transformation are emerging. Thus, it is highly useful for power system electromagnetic transient simulation programs to have integrated capability for wavelet transformation. This paper also briefly presents several applications of wavelet transformation in power system protection and power quality monitoring.

This paper presents a simulation algorithm to simulate the hysteresis characteristics in the core of a power transformer. The algorithm is based on the Jiles–Atherton phenomenological model of a ferromagnetic material. The new transformer model is capable of producing a close representation of the transformer magnetizing current. Comparisons are made between recorded and simulated waveforms using a single phase distribution transformer. A good agreement is achieved between recorded and simulated data.

A hysteresis model based on the Jiles-Atherton theory is incorporated into a power transformer model in an electromagnetic transient program (EMTP)-type program. The eddy current effects are also included in the same model. Comparisons are made between recorded and simulated waveforms using a single-phase distribution transformer. A good agreement is achieved between recorded and simulated data.

This work describes the simulation of the effects of GIC (Geomagnetically Induced Currents) in a power system using a new transformer model. The simulation studies demonstrate that it is important to accurately model the remanence effects in the core of the power transformer.

This paper describes a software model for the time domain simulation of inverse time overcurrent relays. The software model incorporates the IEC and IEEE standard curves, and was developed using Fortran language under the PSCAD platform. The software model simulates the effect of current on an inverse time overcurrent relay, and can be configured to represent various custom-designed overcurrent relays. Extensive tests have shown that the software model can be used to simulate electromechanical, static analog and digital time overcurrent relays with accuracy.

This paper describes the development of an electromagnetic transient model to represent the eddy current effects in transformer magnetising current. The magnetising current of a transformer is both nonlinear and frequency dependent. The frequency dependence is due to eddy currents. The most commonly used method to represent losses in a transformer model is to add a shunt resistance across one winding. In this paper we have extended a hysteresis model based on the Jiles Atherton theory of ferromagnetic hysteresis to include the effects of eddy currents. A comparison of simulation results and test results is presented in the paper.

This paper presents the simulation of multiple current transformers (CTs) operating in parallel into a common spill circuit. The voltage across the spill branch in the high impedance case can be quite high and a varistor (MOV) may be placed across the spill branch to keep this voltage within safe limits.

The hysteresis loop of the core material in a test current transformer is simulated using the Jiles-Atherton theory. Comparisons are made between recorded and simulated waveforms and it is found necessary to replace the modified Langevin function used by Jiles and Atherton. Using an alternative function described in the paper, good agreement is achieved between test and simulated waveforms.